1. Technical Field
The present invention relates to a synchronization device, which is provided in a gear arrangement forming part of a vehicle transmission.
2. Background
A gear box in a vehicle transmission usually has an input rotating shaft and an output rotating shaft. The principal object is to transmit rotation with the possibility of selecting between various rotational gear ratios between the input and output shafts.
The document SE 514231 C2, corresponding to US2003/0110876 A1 and the disclosure of which is expressly incorporated herein by reference, discloses a type of a previously known range gear box of the planetary gearing type, where the ring gear itself is utilized as a clutch sleeve. The ring gear is axially displaceable between a high-range position and a low-range position. A first clutch ring is fixedly connected with a range gear housing and a second clutch ring is fixedly connected with an input shaft of the range gear box. Synchronization rings are provided on either side of the ring gear. On each respective synchronization ring, a garter spring is provided, the purpose of which is to transmit bearing force from the ring gear to the synchronization ring during synchronization and gear changing by means of cooperation with recesses in the ring gear. During a change of the gears, for example from low-range position (low gear) and a large gear ratio to high-range position (high gear) and a smaller gear ratio, the rate of rotation of the ring gear must be adjusted to the rate of rotation of the input shaft before it can be locked to, or be engaged with the input shaft. This is achieved by means of the fact that a bearing force is applied to the ring gear in an axial direction towards the synchronization ring for high-range; i.e., the synchronization ring must adjust the rotation of the ring gear to the rate of rotation of the input shaft. When synchronization of the rotation speed has been achieved, the ring gear is locked to the input shaft because the ring gear now can be axially displaced and engage with the clutch ring for high-range, which clutch ring is rotationally connected with the input shaft. By means of bars for conveyance, which are provided on both synchronization rings, these will always rotate with the ring gear even when the ring gear is axially displaced in relation to the respective synchronization ring. During synchronization and gear changing, the respective garter spring transmits bearing force from the ring gear to the respective synchronization ring by means of cooperation with recesses in the ring gear. Planet wheels are provided on a planet carrier. During its axial movement for engagement of gear, the ring gear will separate the friction surfaces in the synchronization to the gear which is disengaged. This is provided by means of axial surfaces in the recesses on the synchronization ring and the recesses on the ring gear cooperate with the respective garter spring and thereby pull apart the friction surfaces of the clutch ring and the synchronization ring, respectively. Friction losses from trailing synchronization rings are eliminated, which results in a fuel saving. At the same time, the wear on the friction surfaces is also reduced. The synchronization device according to the document SE 514231 C2 results in a wide ring gear and a small freedom to optimize synchronization details and ring gear teeth since they are mutually dependent.
The document SE 450944 B1, corresponding to U.S. Pat. No. 4,667,538 and the disclosure of which is expressly incorporated herein by reference, discloses another example of a two-geared synchronized gear arrangement in a range gear box of the planetary gearing type, where the synchronization for each gear is constituted by a clutch ring, a synchronization ring which cooperates with the clutch ring by means of friction surfaces and is axially displaceable, which synchronization ring is arranged to rotate with an axially displaceable clutch sleeve, and a spring suspension element in the form of a garter spring. In this type of synchronization device, the entire synchronization device is provided on one side of the ring gear of the planetary gearing, which ring gear is fixed to the clutch sleeve. In this case as well, garter springs transmit bearing force from the sleeve to the synchronization ring during synchronization and gear changing by means of cooperation with recesses in the clutch sleeve. In this case as well, a change of gears takes place in a manner which is similar to that for the device according to the document SE 514231 C2. Corresponding bars for conveying both synchronization rings result in that these always rotate with the clutch sleeve even when the clutch sleeve is displaced axially in relation to the respective synchronization ring. This implies that the synchronization ring, which at the moment does not have its rate of rotation adjusted to the associated clutch ring, will lie and trail against its associated clutch ring. Due to the fact that the rates of rotation are different on the synchronization ring and the clutch ring for the non-engaged gear, this results in friction losses as the cone-shaped friction surfaces glide against each other.
The synchronization rings in the document SE 450944 B1 are axially displaceable in relation to the clutch ring and the clutch sleeve. As a result, when the vehicle in which the gear arrangement is provided travels on, for example, uphill slopes or downhill slopes, one of the synchronization rings will trail against its clutch ring, more or less, depending on which axial direction it moves as a result of the force of gravity.
For a similar device as the device for heavy diesel vehicles which is exemplified in the document SE 450944 B1, an average counteracting moment of approximately 2 Nm has been measured from the trailing synchronization ring for low-range, which corresponds to approximately 1 cl diesel fuel per 10 km.
The synchronization device according to the document SE 450944 B1 is also composed of many parts and is therefore comparatively expensive to manufacture and assemble.
Thus, there is a demand for reducing or eliminating friction losses in synchronization devices which are provided in a range gearing where the low-range and the high-range synchronization ring is provided on the same side in relation to the clutch sleeve, as well as for simplifying manufacture and assembly of the arrangement. This is also a principal object of the invention described below.
Devices configured according to the present inventive teachings are based on synchronization devices of the type described hereinabove and which are also referred to in the art as being the locking ring versions of the so-called Borg-Warner-synchronization type. Such devices comprise (include, but are not limited to) a synchronization device of the locking ring type, which are provided in a gear arrangement forming part of a vehicle transmission. The arrangement is intended to, on the one hand, synchronize the rotation speed between a shaft and a ring gear which is coaxially arranged in relation to the shaft and forms part of a planetary gearing, and on the other hand, forms part of the gear arrangement between the ring gear and a gear housing. The synchronization device comprises a first clutch ring which is fixed to the shaft and a second clutch ring which is fixed to the gear box housing. At least one synchronization ring is also included that cooperates with the clutch rings by means of friction surfaces and is axially displaceable; the synchronization ring is arranged to rotate with an axially displaceable clutch sleeve. The clutch sleeve is fixed to the ring gear. At least one spring suspension element is provided that transmits bearing force from the clutch sleeve to the synchronization ring during synchronization and gear changing by means of cooperation with first recesses in the clutch sleeve. The clutch sleeve, clutch rings, synchronization ring, and the spring suspension element are provided on one side of the ring gear. The synchronization device is characterized in that one of the synchronization rings is constructed together with an additional mirror-inverted synchronization ring in order to form a double synchronization ring. Further, the clutch sleeve during its axial movement for gear engagement separates the friction surfaces in the synchronization device to the gear which resultingly become disengaged because at least one second recess is provided on the double synchronization ring and the spring suspension element cooperates with the second recess as well.
In this way, apart from the advantage regarding elimination of friction losses due to trailing synchronization rings, there is also the benefit make possible by the reduction in the number of included parts in a gear arrangement.